U.S. patent number 5,470,322 [Application Number 08/227,954] was granted by the patent office on 1995-11-28 for reinforced multilumen catheter for axially varying stiffness.
This patent grant is currently assigned to Danforth Biomedical Inc.. Invention is credited to Michael J. Horzewski, Nitin P. Matani.
United States Patent |
5,470,322 |
Horzewski , et al. |
November 28, 1995 |
Reinforced multilumen catheter for axially varying stiffness
Abstract
Multilumen catheters are provided with an axially decreasing
stiffness by the incorporation of a hollow tube formed of a
relatively stiff material into the catheter construction. The tube
may either encircle the catheter as an external shell or reside
inside one of the lumens as a liner. The stiffness variation may be
attained by extending the hollow tube only part of the distance
from the proximal to the distal ends of the catheter or by varying
the construction of the hollow tube.
Inventors: |
Horzewski; Michael J. (San
Jose, CA), Matani; Nitin P. (San Jose, CA) |
Assignee: |
Danforth Biomedical Inc. (Santa
Clara, CA)
|
Family
ID: |
22855137 |
Appl.
No.: |
08/227,954 |
Filed: |
April 15, 1994 |
Current U.S.
Class: |
604/524 |
Current CPC
Class: |
A61M
25/0054 (20130101); A61M 2025/0037 (20130101) |
Current International
Class: |
A61M
25/00 (20060101); A61M 025/00 () |
Field of
Search: |
;604/96-103,43-45,280,282 ;606/192,194 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0279959A1 |
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Aug 1988 |
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EP |
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0421650A1 |
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Apr 1991 |
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EP |
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5253304 |
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Oct 1993 |
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JP |
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WO92/07507 |
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May 1992 |
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WO |
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WO93/02733 |
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Feb 1993 |
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WO |
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WO93/20881 |
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Oct 1993 |
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WO |
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WO93/23107 |
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Nov 1993 |
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WO |
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Primary Examiner: Yasko; John D.
Assistant Examiner: Cermak; Adam J.
Attorney, Agent or Firm: Townsend and Townsend and Crew
Claims
What is claimed is:
1. A multilumen medical catheter for insertion into a body cavity
through elongated and convoluted narrow passageways in the body,
said medical catheter comprising:
a shaft having proximal and distal ends;
a functional element at said distal end of said shaft;
a plurality of lumens extending axially through said shaft;
first and second hollow tubes of material substantially more rigid
than said shaft and affixed thereto, said hollow tubes extending
from said proximal end of said shaft to differing distances toward
said distal end, thereby cumulatively imparting to said shaft a
stiffness varying in stepwise manner, progressing from a maximum
stiffness at the proximal end of said shaft top a minimum stiffness
at the distal end of said shaft, said first hollow tube being
disposed inside one of said lumens and said second hollow tube
being disposed inside another of said lumens.
Description
This invention relates to medical catheters designed for insertion
into bodily cavities through long and convoluted passageways.
BACKGROUND OF THE INVENTION
Many medical procedures involve the insertion of catheters through
bodily lumens such as blood vessels, nasal passages, urethral
passages and the like to reach cavities or regions of the body
where a therapeutic function is to be performed. Often, the lumens
are convoluted or branched, particularly in the case of blood
vessels, and insertion of the catheter so that its distal end
reaches the desired location involves steering and maneuvering of
the catheter through delicate, narrow passages, and the bending and
curving of the catheter to conform to the shapes of the passages.
This quality of the catheter is commonly referred to as
"steerability." Many of the sites sought to be reached are also a
considerable distance from the point of entry of the catheter into
the body. Pushing the catheter shaft in far enough to reach these
sites requires that the shaft be stiff enough so that it will not
bend back over itself or form kinks. The term "pushability" has
been used to characterize this quality. To accommodate these two
needs, catheters have been constructed in different ways to achieve
a proximal end which is stiffer than the distal end, and many of
these constructions are complicated and expensive to
manufacture.
Multilumen catheters offer even greater problems since they are of
larger diameter than single-lumen catheters and require open space
for the lumens. The open space reduces the amount of
cross-sectional area and hence the opportunity for the
incorporation of structural features to add to or vary the
stiffness of the catheter shaft.
SUMMARY OF THE INVENTION
These and other needs are addressed by the present invention, which
resides in multilumen catheter shafts with a stiffness that varies
along the length of the shaft, thereby providing both pushability
and steerability, and thus the capability of inserting the
catheters through long bodily passages which terminate in
convoluted, closely bent or curved, or intricately branched regions
prior to or at the site of the region where the presence of the
functional tip of the catheter is required. Axial variation in the
stiffness of these catheter shafts is provided by the incorporation
of a hollow tube into the construction of the shaft, the tube
material having greater stiffness than the material of which the
remainder of the catheter is constructed. The hollow tube may
itself vary in stiffness, or it may extend less than the full
length of the catheter shaft such that the tube imparts an increase
in stiffness only to the proximal segment of the catheter which the
tube occupies. For a tube which itself varies in stiffness, the
variation can be achieved either by a variation in the material of
construction used for the tube, or by the thickness of the tube.
The variation can be stepwise, with two or more steps, or
continuous, either in a linear or nonlinear manner. The axial
variation in stiffness can also be achieved by the use of two or
more tubes, all beginning at the proximal end but differing in
length, again providing a stepwise variation in stiffness. In any
of these various embodiments of the invention, the tube(s) may
either form the exterior surface of the catheter shaft or form a
lining in one or more of the lumens.
The use of a hollow tube or tubes in accordance with this invention
offers the advantage of introducing a relatively stiff material of
construction which may be unsuitable for use at the distal tip of
the catheter, where greater flexibility is needed. The tube
material will be sufficiently stiff that any increase in the
catheter diameter when the tube surrounds the outer circumference
of the catheter, or any decrease in the cross section of a lumen
when the tube is a lining for the lumen, is small enough to have at
most a minimal effect on the diameter of the catheter or the width
of the lumen. Another advantage offered by the hollow tube is that
it adds to the hoop strength of the catheter, lessening its
tendency to expand or rupture due to a high pressure fluid inside
one or more of the lumens.
The lumens of catheters in accordance with this invention remain
available for use for a variety of functions, including
accommodating guidewires, passing drugs and other fluids used for
perfusion of the bodily cavity, draining fluid from the bodily
cavity, or, in the case of balloon-tipped catheters, passing a
pressurized inflation fluid to the distal end of the catheter to
inflate the balloon.
Details of these and other features of the invention and preferred
embodiments will be apparent from the description which
follows.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a depiction of a catheter which may incorporate the
features of the present invention.
FIG. 2 is a longitudinal cross section of a segment of a catheter
like that of FIG. 1, illustrating one embodiment of the
invention.
FIG. 3 is a transverse cross section of the catheter whose
longitudinal cross section is shown in FIG. 2.
FIG. 4 is a longitudinal cross section of a segment of another
catheter like that of FIG. 1, illustrating a second embodiment of
the invention.
FIG. 5 is a transverse cross section of still another catheter,
illustrating a third embodiment of the invention.
FIG. 6 is a transverse cross section of the catheter of FIG. 5,
taken at a different axial location along the catheter.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
While this invention is generic in scope, it will be best
understood by a detailed discussion of specific embodiments.
FIG. 1 depicts a catheter 11 in which the invention may be
incorporated. This is one of many different types of catheters for
a wide variety of uses, all of which can benefit from the present
invention. The catheter depicted in FIG. 1 is a balloon angioplasty
catheter for coronary angioplasty procedures. The catheter includes
an elongated shaft 12 with proximal 13 and distal 14 ends, and a
dilatation balloon 15 at the distal end. Any of a wide variety of
other functional elements may be substituted for the balloon, or
incorporated in addition to it. Furthermore, additional fixtures
and connections not shown in the drawing will be included at the
proximal end 13 to serve as fluid connections and to facilitate
manipulation of the catheter, positioning of the distal end,
inflation and deflation of the balloon 15, and/or activation of any
additional functional elements at the distal end (not shown). In
accordance with the invention, the shaft 12 varies in stiffness
along its length, with the proximal end 13 regions exhibiting a
relatively high stiffness, which decreases either gradually or in
stepwise manner toward the distal end 14.
An enlarged longitudinal cross section of a segment of the catheter
is shown in FIG. 2. The catheter is shown to have two lumens 21,
22, both extending the full axial length of the catheter shaft.
Catheters within the invention may also contain three or more
lumens. Also, the lumens in the catheter shown in FIG. 2 are
neither coaxial with the catheter axis nor with each other. The
invention also extends to multilumen catheters in which one or more
of the lumens are annular in shape.
The segment shown in the drawing is in the region where a
transition in stiffness occurs from a proximal region of relatively
high stiffness 23 to a distal region of lesser stiffness 24. While
the shaft body itself 25 extends the full length of the shaft, the
proximal region 23 is made stiffer by the hollow tube 26 of denser
and stiffer material which encircles the shaft body and terminates
at the transition point between the two regions. The distal
terminus 27 of the hollow tube is tapered to form a smooth
transition. A transverse cross section of the high stiffness region
23 of the shaft is shown in FIG. 3.
An alternative means of achieving proximal and distal regions of
differing stiffness is shown in FIG. 4. In this construction, the
hollow tube 31 extends the full length of the shaft, but the tube
itself is in two segments, a proximal segment 32 and a distal
segment 33. The variation in stiffness is achieved by a variation
in the material of construction between these two segments, or the
manner in which the material is extruded or treated in forming the
two segments. In either case, all parts of the hollow tube are of
the same wall thickness and are stiffer than the interior portion
34 constituting the remainder of the shaft material.
FIGS. 5 and 6 depict a third means of achieving proximal and distal
regions of differing stiffness in the catheter shaft. These two
drawings represent transverse cross sections of the catheter shaft
at two different locations along the shaft axis, FIG. 5
representing a location in the proximal region where the greater
stiffness is required, and FIG. 6 representing a location in an
intermediate region where the stiffness is intermediate between
that of the proximal and distal regions.
The construction shown in FIGS. 5 and 6 differs from those of FIGS.
2 and 3 in several ways. First, while the catheter contains two
lumens 41, 42, both lumens in this construction are of circular
cross section. Second, there are two hollow tubes 43, 44 rather
than just one, one of the tubes 43 being longer than the other and
extending into the intermediate region while the other 44
terminates at the distal end of the proximal region. The longer
hollow tube 43 terminates at the distal terminus of the
intermediate region and does not extend into the distal region.
Third, both hollow tubes 43, 44 reside inside the lumens rather
than encircling the entire catheter shaft. Each hollow tube is of a
constant wall thickness and stiffness, and the variation in
stiffness of the catheter shaft is in two stages, the two tubes a
cumulative stiffening effect in the proximal region, the single
tube being the sole stiffening element in the intermediate region,
and the absence of such tubes in the distal region leaving that
region the least stiff of the three.
As a further alternative, FIGS. 5 and 6 may represent two
independent catheters (rather than cross sections at two different
axial locations on a single catheter). According to this
alternative, only one lumen in the catheter of FIG. 6 contains the
reinforcing hollow tube while both lumens in the catheter of FIG. 5
contain reinforcing hollow tubes.
Although not shown in the drawings, a still further means of
achieving a decrease in stiffness along the length of the shaft is
by narrowing the wall thickness of the hollow tube toward the
distal end of the shaft. This may be done stepwise or in a
continuous manner.
The dimensions of the catheter, its shaft, the lumens and the
hollow tube are not critical and may vary widely depending on the
functions which the catheter is designed to serve and the
particular type or configuration of bodily vessel or cavity which
the catheter is to be used in. The length of the catheter, for
example, will be within typical ranges of catheters as they are
currently in use in medical procedures or have been disclosed in
the literature. For catheters intended to be used in a patient's
vasculature, the length of the catheter shaft will most often be at
least about 100 cm, and preferably at least about 120 cm. The outer
diameter of the catheter shaft in most cases will be from about
0.01 inch (0.0254 cm) to about 0.1 inch (0.254 cm). Typical balloon
angioplasty catheters are approximately 135 cm in length, including
the balloon, and an outer diameter of approximately 0.04 inch
(0.102 cm). For hollow tubes which do not extend the full length of
the shaft, the distal terminus of the hollow tube will most often
be at least about 20 cm from the distal end of the shaft, and
preferably at least about 30 cm from the distal end of the shaft.
The wall thickness of a hollow tube will most often be within the
range of about 0.001 inch (0.00254 cm) to about 0.01 inch (0.0254
cm). It is presently contemplated that for catheter shafts of
approximately 135 cm in length and an outer diameter of about 0.04
inch (0.102 cm), a typical hollow tube will have a length of about
100 to about 110 cm and a wall thickness of about 0.002 to about
0.003 inch (0.0051 to 0.0076 cm).
The materials of construction may vary widely, the primary criteria
being the stiffness range and the difference in stiffness between
the shaft material and the hollow tube material. Prime examples of
materials for the shaft are polyethylene and polyurethane, although
any readily formable or extrudable material from which a shaft with
dimensions and lumens of the requisite precision can be made may be
used. Examples of materials of construction for the hollow tube are
polyimide, hypotube (a stainless steel containing nickel and
titanium as alloying components), polytetrafluoroethylene and
related materials known as TEFLON, high density polyethylene, and
composites of these materials.
The hollow tube can be secured to the catheter shaft by any of a
variety of methods. Examples are lamination, co-extrusion, dip
coating, adhesive bonding, and a tolerance fit. Methods of
effecting these techniques are well known in the art.
The foregoing is offered primarily for purposes of illustration. It
will be readily apparent to those skilled in the art that the
materials, dimensions, configurations and other parameters of the
catheter may be further modified or substituted in various ways
without departing from the spirit and scope of the invention.
* * * * *